1. Field of the Invention
The present invention generally relates to a method and system for accepting or rejecting a spoken dialog hypothesis. More particularly, the present invention relates to a method and system for determining acceptance of a spoken dialog hypothesis by comparing a confidence level to a threshold that is based upon the type of hypothesis.
2. Description of the Related Art
Spoken dialog systems need to determine whether to accept or reject a hypothesis. For example, a spoken dialog system may receive a sound signal representing the voice of a user of the system and the system may then compare the input signal to potential candidates. The system would determine a hypothesis by, for example, selecting a candidate from a list of candidates that has the highest confidence indicator. However, these systems need to determine whether the confidence indicator is high enough such that the system should accept the hypothesis as being correct. It is undesirable to automatically accept a hypothesis merely because it has the highest confidence of all potential candidates because the candidate with the highest confidence level may have a relatively low confidence level. These conventional systems address this problem by comparing the confidence level of a hypothesis to a predetermined threshold. If the confidence level exceeds the predetermined threshold, then the hypothesis is accepted. If the confidence level does not exceed the predetermined threshold, then the hypothesis is rejected. In this manner, conventional systems attempt to avoid making wrong decisions.
Some conventional systems attempt to further reduce the chance of an incorrect acceptance by providing two different thresholds. These systems incorporate a rejection threshold and a confirmation threshold. The rejection threshold is always lower than the confirmation threshold. Any hypothesis having a confidence level below the rejection threshold is rejected. Any hypothesis having a confidence level above the rejection threshold, but below the confirmation threshold requires that the user confirm whether the hypothesis is correct before the hypothesis is accepted by the system. Any hypothesis having a confidence level above the confirmation threshold is accepted without confirmation.
One conventional system derives features about a hypothesis from a recognizer and a parser and then classifies these features to determine whether to accept or reject the hypothesis. This system is concerned more with efficient operation rather than achieving the correct result.
Another conventional system adjusts acceptance thresholds based upon the length of the input audio. Since this system only considers the duration of the input audio, the system does not rely upon any hypothesized information at all to make a threshold determination.